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We report a yolk-shelled anode material with an MoS2/C core, large inner void and C@MoS2 shell (MoS2/C@Void@C@MoS2). This design could accelerate Na+/K+ reaction kinetics and endure volume changes. Based on the kinetics analysis and calculations based on density functional theory, this structure could effectively enhance the high-rate sodium/potassium storage capability. [ABSTRACT FROM AUTHOR]

Layered transition metal chalcogenides (MX, M=Mo, W, Sn, V; X=S, Se, Te) have large ion transport channels and high specific capacity, making them promising for large‐sized Na+/K+ energy‐storage technologies. Nevertheless, slow reaction kinetics and huge volume expansion will induce an undesirable electrochemical performance. Numerous efforts have been devoted to designing MX anodes and enhancing their electrochemical performance. Based on the metal‐organic assembly strategy, nanostructural engineering, combination with carbon materials, and component regulation can be easily realized, which effectively boost the performance of MX anodes. In this Review, we present a comprehensive overview on the synthesis of MX nanostructure using the metal‐organic assembly strategy, which can realize the design of MX nanostructures, based on self‐sacrificial templates, host@guest tailored templates, post‐modified layer and derivative templates. The preparation routes and structure evolution are mainly discussed. Then, Mo‐, W‐, Sn‐, V‐based chalcogenides used for Na+/K+ energy storage are reviewed, and the relationship between the structure and the electrochemical performance, as well as the energy storage mechanism are emphasized. In addition, existing challenges and future perspectives are also presented. [ABSTRACT FROM AUTHOR]

Core–shell structures with gradient components are considered as promising active materials for energy storage systems because of their prominent synergistic effects and enhanced reaction kinetics. In this work, gradient-structured VSe1.6/C@N–C⊂MoSe2 nanotubes, with VSe1.6/C inner cores, and double shells of protecting N–C layers and an activated MoSe2 outer shell, are prepared through a high-temperature selenization process of a tailored template, which are obtained from an organic–inorganic assembly process. As for the storage of the large-sized Na+/K+ ions, this ingenious structure of VSe1.6/C@N–C⊂MoSe2 nanotubes can markedly enhance the reaction kinetics and well balance the reaction activity and cycling stability, due to increased ion/electron diffusion channels from the MoSe2 and N–C shells, abundant internal interfaces and gradient-component distribution. As a result, a capacity of 232.4 mA h g−1 over 10 000 cycles can be retained at a current of 5.0 A g−1, with a capacity retention of 86.8%. As for potassium ion batteries (PIBs), VSe1.6/C@N–C⊂MoSe2 nanotubes deliver a high and stable capacity of 180 mA h g−1 at 1.0 A g−1 for 5000 cycles with a capacity retention of 71.3%. Based on dQ/dV analysis and ex situ XRD results, the VSe1.6/C@N–C⊂MoSe2 anode has a hybrid mechanism of MoSe2 (intercalation and conversion reactions) and VSe1.6 (only intercalation reaction) and high reversibility for K+ storage. And combined with the component and structural superiorities, high cycling stability can be achieved for the VSe1.6/C@N–C⊂MoSe2 nanotubes in PIBs. [ABSTRACT FROM AUTHOR]

Few-layered MoSe2 nanosheets are significant for energy storage due to more active edges and improved conductivity. Herein, the cavity confinement effect of structure-defected UiO-66-NH2 is applied to host H3PMo12O40 units, which can be transformed into few-layered MoSe2 nanosheets confined into N,P-doped carbon polyhedrons (MoSe2/N,P-C) for fast Na+/K+-ion storage. Also, this unique architecture can provide sufficient active sites, alleviate the mechanical strain, and offer spacious channels for Na+/K+-ion transfer. Particularly, MoSe2/N,P-C-(5:1) possesses superior sodium storage capability (316 mA h g–1 at 2.0 A g–1 within 300 cycles), promoted by the accelerated reaction kinetics and capacitive effect. In addition, an ultralong cycling stability with an expected capacity of 177 mA h g–1 (1.0 A g–1 after 1000 cycles) and a high rate capability (139.9 mA h g–1 at 10.0 A g–1) can be achieved for the K+-ion storage. Ex situ Raman spectra and X-ray diffraction analysis imply a combined mechanism of a reversible intercalation–conversion process for active MoSe2 and partial reversibility of the N,P-C skeleton. In addition, the assembled MoSe2/N,P-C//Na3V2(PO4)3/C full cell also exhibits a capacity of 322.5 mA h g–1 at 0.5 A g–1, implying the potential application in practice. [ABSTRACT FROM AUTHOR]